Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$228.43	13.859%	$260.0881	$260.09	$260.10	$260.10
Purchase #2	$40.91	9.638%	$44.8529	$44.85	$44.85	$44.90
Purchase #3	$223.99	10.869%	$248.3355	$248.34	$248.35	$248.30
Purchase #4	$61.87	9.275%	$67.6084	$67.61	$67.60	$67.60
Purchase #5	$119.86	3.355%	$123.8813	$123.88	$123.90	$123.90
Purchase #6	$246.88	6.734%	$263.5049	$263.50	$263.50	$263.50
Purchase #7	$92.53	5.293%	$97.4276	$97.43	$97.45	$97.40
7 purchase totals =	$1,014.47		$1,105.6987	$1,105.70	$1,105.75	$1,105.70